1. Field of the Invention
The present invention relates to an image forming apparatus, such as an electrophotographic copying machine or printer.
2. Description of the Prior Art
Conventionally, coupled rollers for fixing an image in an image forming apparatus, such as an electrophotographic copying apparatus or the like, is so disposed that the nip formed by the coupled rollers extends parallel with an axis of a photosensitive drum. The photosensitive drum receives a transfer material, at its image transfer station, so that the leading edge of the transfer material is parallel with the axis of the photosensitive drum, or perpendicular to the direction of the transfer material movement. The transfer material receives an image from the photosensitive drum at the image transfer station and then is conveyed to coupled fixing rollers by suitable conveying means, while the leading edge thereof is kept parallel with the axis of the photosensitive member. The leading edge is then gripped by the nip of the rollers uniformly over the length of the nip, and the transfer material is subjected to the image fixing operation, whereafter it is discharged to a tray. Thus, the leading edge of the transfer material moves, at all times, parallel to the axis of the photosensitive drum and the nip of the fixing rollers.
Recently, there is a trend of reducing the size and cost of the image forming apparatus, which leads to decreasing the distances between the transfer material feeding roller, the registering rollers, the photosensitive drum, the separating roller, the conveying rollers and the fixing rollers, respectively. The decrease in such distances results in the stricter confinement on the transfer material. Particularly, the size reduction necessiates the decrease of the distance between the transfer material separating station to the fixing station. To secure a certain distance therebetween, the passage of the transfer material has to be curved, not straight. Further, when the transfer material is conveyed with only one of its lateral ends being guided along a predetermined path, the leading edge of the transfer material may be gripped unevenly over the nip. This may result in wrinkles in the transfer material, the jamming thereof or other various troubles caused by the wrinkles.